1. Field of the Invention
This invention relates to a television receiver, or in particular to a television receiver capable of functionally switching the operation power supply.
2. Description of the Related Art
As is well known, the digital TV broadcast has started also on the terrestrial wave, and digitization of all types of broadcasts is planned. Along with this trend, the TV receiver to receive the broadcast is required to have a circuit configuration adapted to process the received digital broadcast signals.
The received signal selected by the tuner, for example, is first demodulated and after error correction, descrambled and other processes, separated into packets by a demultiplexer. At the same time, the digital video data and the digital audio data are decoded and converted into non-compressed digital signals. The video signal is converted into an analog signal as required and supplied to a video display, while the audio signal is converted into an analog signal and output through output means such as a speaker.
In the TV receiver compatible with the digital broadcast described above, the signal processing is complicated, and as compared with the signal processing for the analog broadcast, a longer time is required for signal processing. Once the power supply of the receiver is turned off, therefore, not a small amount of time is required before the normal operation of the receiver is restored. In the case where the power supply is turned off erroneously while a program is being viewed, for example, the suspension of viewing the particular program is unavoidable until it becomes viewable again.
Also, with regard to the liquid crystal panel now widely used as a video display, once the power for the control circuit to control the drive operation of the display fails, the power restoration consumes a considerable time and the need of more proper power management is pointed out.
The ordinary TV receiver includes a remote control as standard equipment, which is exclusively used to switch the channel of the receiver, set the volume control and other operations and various adjustments. Even the power can be switched on and off by the remote control.
In the case where the power fails by the erroneous power key operation on the remote control while viewing a program, it takes some time before the image is displayed especially on the digital TV receiver after switching on power again. This causes the user irritation and is never considered convenient for the user.
A similar problem is also posed by the TV receiver having a cathode ray tube as a display with regard to the starting characteristic thereof, on which an improvement effort is under way.
Jpn. Pat. Appln. KOKAI Publication No. 5-161093, for example, discloses a system in which the cathode ray tube is kept cut off for a predetermined time after the timing at which the power is turned off by operating the power key of the remote control, while at the same time muting the sound. Thus, the system is apparently set in the same mode as if power is turned off, and in the case where the power key is operated within a predetermined time, the cutoff state of the cathode ray tube and the voice mute mode are canceled in preparation for immediate resumption of viewing. In the case where the power key fails to be operated for longer than a predetermined time, on the other hand, the normal power turnoff process is executed.
In the proposition disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-161093, however, the power circuit is controlled so that the video signal is displayed in black during the standby period of a predetermined time. Therefore, power consumption cannot be reduced sizably, and the control operation is simply the activation or the deactivation of the power circuit, thereby making the functional control impossible.
Further, Jpn. Pat. Appln. KOKAI Publication No. 5-161093 assumes that the TV receiver can be activated quickly by turning on the power switch within a predetermined muting time. Nevertheless, the user cannot be informed of the time point to which and how long the starting time can be shortened after turning off power.
Another problem is that the user cannot be informed of the availability of such a function in the TV receiver from the external appearance thereof.
As described above, in the case where the user turns off the power of the conventional TV receiver by error, the proposition so far made to shorten the time before restarting the display after switching on power still fails to obviate the inconvenience of the user.